PROJECT SUMMARY/ABSTRACT: Aneurysmal subarachnoid hemorrhage (aSAH) is a significant public health problem affecting nearly 30,000 Americans annually and causing long-term functional impairments. Accounting for 25% of all stroke-related deaths, aSAH is a devastating injury that leaves an astounding 66% of survivors with a reduced quality of life and approximately 50% remaining fully dependent on caregivers. It is widely accepted that the poor functional outcomes following aSAH are due in large part to the development of secondary complications during the acute recovery phase including delayed cerebral ischemia (DCI). Unfortunately, the causes of DCI remain largely unknown and studies to develop therapeutic interventions are hindered by the inability to identify patients at high risk for DCI. Preclinical models have elucidated metabolic mechanisms that contribute to a unique type of cell death which is dependent upon intracellular iron and results in secondary ischemic brain injury (similar to DCI) in animals following aSAH. These studies also demonstrate that iron chelators effectively reduce neuronal cell death associated with this complication. Despite this evidence, iron homeostasis is not recognized as an important clinical pathway post-aSAH due to a dearth of research in humans. Based on evidence from our studies as well as the literature, we propose that the substantial variability in patient outcomes following aSAH largely centers on genetic/epigenetic variation in the iron homeostasis pathway; our overall goal is to gain a better understanding of these biological mechanisms. The specific aims of the proposed research are: 1) to characterize the relationship between changes in cerebrospinal fluid DNA methylation of candidate genes related to iron homeostasis and variability of acute and long-term outcomes following aSAH and 2) to examine the relationship between polymorphisms in candidate genes related to iron homeostasis and variability of acute and long-term outcomes following aSAH. Using biospecimens linked to extensive patient outcome phenotype data collected from a large, ongoing longitudinal study, the proposed research will use multiple logistic regression modeling, trajectory modeling, candidate gene association, and gene-gene interaction analyses to explore epigenetic and genetic variability of iron homeostasis pathway. The proposed study is in line with the mission of NINR in that it focuses on improving the health of individuals by deciphering the genetic influence on variability in symptoms and patient outcomes and specifically addresses many of the symptom science innovative questions included in the NINR strategic plan including elucidating the omic indicators related to the mechanisms and assessment of symptoms and the mechanistic pathways that can distinguish underlying symptom cluster trajectories. This novel study will lay the foundation for a line of research to identify clinically relevant biomarkers and evidence- based therapies for aSAH victims in order to improve patient outcomes and also represents a beginning step in the applicant's program of research.